Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Stay patient and give the snowpack time to adjust to this past week’s large load. Stay off open slopes greater than 35 degrees and pay special attention to slopes that are wind-affected or receive direct sunlight. Any avalanche has the ability to grow large enough to bury and kill you.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    The past week has produced storm after storm in the West South, with the volcanoes outpacing areas closer to the crest in terms of water numbers. All areas of the zone saw significant snow depth growth over this time period, and with that volume of snow over a relatively short period of time, the snowpack will need time to adjust. Any triggered avalanche on Thursday could entrain enough snow to be large enough to injure, bury, or kill you, with some isolated slides growing very large and destructive. The best indicator of avalanche potential is recent avalanches and we have had a lot of them the past week. So stick to terrain less than 35 degrees and give the snowpack a bit more time to heal. As winds increase later in the day, take note of wind-affected slopes where slabs could be thickened and possibly more reactive. You can use test slopes to test the most recent storm interface but will need to dig in order to get all the information you need from this past week’s storm parade.

    (1/3/2021) Up track tests like this can highlight weak layers in the new snow. However, they only work as deep as your skis, snowshoes, or machine sinks into the snow. Other weak layers could hide deeper.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    With a lull in the active weather on Thursday, there’s a possibility of some sunshine. We’re not sure if there will be enough of a window of sun effect to drive a Loose Wet avalanche problem, but it should be on your radar. If you find yourself in the sun and the snow surface is getting wet and sticky, you should head for shadier slopes. Loose Wet avalanches may be difficult to get moving, but once they do, they can entrain lots of snow and grow very large, even triggering slabs as they descend. At a minimum, you should be aware of other dangers caused by the sun on Thursday, such as tree bombs. There is a lot of snow currently sitting in the trees, and with warming temperatures, these large masses could fall. Apart from the hazard of being hit by one directly, they could act as triggers when they hit the slopes, triggering slabs or loose avalanches.

    (1/6/2021) In the neighboring Snoqualmie Pass zone on Wednesday, crowns were visible from a natural cycle that occurred overnight, shedding the latest round of storm snow. On a return through the terrain in the afternoon, new rollerballs were observed from warming and light rain, crossing the previous skin track.

Avalanche Discussion

It has been a wild week in the West South which has really highlighted the variability within our zone and has hardly given us time to catch our breath. With so much active weather, it's no wonder we have some uncertainty around conditions, particularly at upper elevations and on the volcanoes where access has been difficult. If you take advantage of the lull in the weather to travel to these areas on Thursday, please submit a public observation to let us know what you find.

Even with a bit of uncertainty, the hazard is easy to manage in some respects. With that much snow over a relatively short period of time, just continue to give the snowpack time to adjust before stepping out into avalanche prone terrain. If you’re looking to pinpoint where and how avalanches may fail, things get a bit harder. There are multiple potential weak layers that could fail in the upper snowpack, which ranges from 3-6 feet across the zone. Maybe the most sensitive layers have already failed during the continuous avalanche cycle the past few days. Maybe some are still waiting for you to come along and be the weight that pushes them over the edge. Crystal Pro Patrol reported triggering slabs as deep as 3 feet in wind affected terrain on Wednesday, which has become the norm over the past week. As we start to make our way into the mountains more and get some visibility around the zone, the signs of avalanches from the past week continue to present themselves to us. In the neighboring Snoqualmie Pass zone, large slides have been observed in windows of clear weather that have broken into deeper layers of the snowpack. These slides highlight the potential for some isolated very large and destructive avalanches to occur.

As you dig around to find out what’s happening in the snow for yourself, two layers serve as notable snowpack markers for you. On New Years Day, a crust was formed and buried in most areas of the zone. We believe that most of the daily avalanche activity has not gone below this layer and that to continue for Thursday. The prominent 12/21 crust still serves as a reference as the de-facto start of this storm cycle. 

In addition to dangerous avalanche conditions, non-avalanche hazards exist out there. Creeks are running high at lower elevations, large amounts of snow and branches are falling from trees, and the deep snow is a hazard due to tree wells and deep snow immersion. Find out more information about deep snow safety HERE.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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